JP5055008B2 - Actuator - Google Patents

Description

  The present invention relates to an actuator using a piezoelectric body, and more particularly to an actuator that can be efficiently driven with a large driving force.

A conventional actuator has a long cylindrical nut having a piezoelectric element mounted on the outer surface and a shaft having a screw screw on the outer peripheral surface, and the shaft is inserted inside the nut. When ultrasonic vibration is applied to the nut, the nut causes torsional movement, and the shaft is moved back and forth in the axial direction.
US Pat. No. 6,940,209

  The actuator described in Patent Document 1 is driven in a state where the drive frequency of the drive signal is matched with the resonance frequency (self-resonance point) unique to the actuator.

  However, the resonance frequency is easily affected by the temperature change of the actuator, and when the ambient environmental temperature fluctuates, there is a problem that the resonance frequency shifts from the intended drive frequency and the drive efficiency is lowered.

  Further, the device described in Patent Document 1 has a configuration in which ultrasonic vibration is applied to the nut to move the shaft forward and backward in the axial direction. Generally, a nut is difficult to be deformed because its diameter is larger than that of a shaft. For this reason, there is a problem that the nut is not driven according to the drive signal, and it is difficult to increase the efficiency of moving the shaft that is a movable body.

  The present invention has been made to solve the above-described conventional problems, and an object of the present invention is to provide an actuator that can be driven efficiently without matching the drive frequency of the drive signal with the resonance frequency on the actuator side.

  It is another object of the present invention to provide an actuator that can efficiently drive a nut serving as a movable body by applying vibration in the rotational direction to a shaft that is thin and easily deformed.

The present invention includes a shaft having a male thread on the outer circumference extending in the axial direction, the shaft and the movable member through-hole that meshes with the male screw is inserted is formed, the vibration generating mechanism giving rotational vibration around the axis of said shaft And a drive circuit for driving by giving a predetermined drive signal to the vibration generating mechanism ,
The vibration generating mechanism is provided with a plurality of piezoelectric elements that apply a rotational force in the forward direction and a rotational force in the reverse direction around the axis to the shaft by expansion and contraction, and the same from the drive circuit to the plurality of piezoelectric elements A driving signal is given synchronously, a plurality of the piezoelectric elements expand and contract simultaneously, and a rotational force in the forward direction and a rotational force in the reverse direction are repeatedly applied to the shaft,
One of the time for applying the rotational force in the forward direction and the time for applying the rotational force in the reverse direction is set shorter than the other time, and the movable member is moved in the axial direction. Is.

  In the present invention, the nut serving as the movable member can be moved in the axial direction by driving the shaft by applying rotational vibration in the direction around the axis. By vibrating the shaft, which is a member having a small diameter, it is possible to efficiently move the movable body forward and backward in the axial direction.

  With the above means, it is possible to drive efficiently with a larger driving force. In addition, since all the piezoelectric bodies are driven by one drive signal, it is not necessary to match the drive frequency of the drive signal and the resonance frequency on the actuator side, and the problem of reduction in drive efficiency due to frequency deviation can be eliminated.

  In the above, the piezoelectric body may be a single layer type composed of a single piezoelectric element or a multilayer type in which a plurality of piezoelectric elements are laminated.

  In the case of a single layer type, a vibration generating mechanism suitable for downsizing or thinning can be provided. On the other hand, in the case of the laminated type, the displacement amount and driving force in the thickness direction of the entire piezoelectric body can be made larger than that of the single layer type.

  Further, it is preferable that a cap made of a convex surface or a hemispherical surface protruding toward the distal end is provided at the distal end of the movable member.

  In the above means, even if the tip of the movable member comes into contact with any member, the rotation of the movable member itself does not stop, and vibration in the rotation direction can be continuously performed.

  Furthermore, a male screw is formed on one of the surface of the shaft and the inner surface of the through-hole, and a female screw is formed on the other, and a predetermined distance between the male screw and the female screw and in a radial direction orthogonal to the axial direction is predetermined. Those provided with a clearance of 2 are preferable.

  In the above means, when the rotational speed of the shaft is low, the movable member rotates together with the shaft. However, when the shaft is reversed at high speed, only the shaft rotates, so that the movable member can be moved in the axial direction.

  Moreover, it is preferable that the base of the movable member and the outer surface of the shaft are respectively provided with stoppers that engage with each other.

  In the above means, the movable member to the proximal end portion side of the shaft can be restricted and the movable member can be prevented from being locked to the shaft, so that the driving efficiency can be prevented from being lowered.

  In the actuator according to the present invention, it is possible to efficiently drive the nut serving as the movable body by applying vibration in the rotational direction to the shaft side whose diameter is thin and easily deformed. For this reason, it is not necessary to force the drive frequency of the drive signal to coincide with the resonance frequency on the actuator side.

FIG. 1 is a perspective view of an actuator showing a first embodiment of the present invention.
Since the actuator according to the present invention exerts a large driving force, it can be used as a means for moving a camera lens mounted on a mobile phone along the optical axis direction, for example. Absent.

First, the configuration of the first exemplary embodiment of the present invention will be described.
As shown in FIG. 1, the actuator 10 shown in the first embodiment includes a shaft 11 extending in the axial direction (Z direction), a movable member 12 movably provided in the axial direction of the shaft 11, and a movable member. A vibration generating mechanism 20 that generates vibration for moving the member 12 is provided.

A male screw 11a having a predetermined pitch is formed on one (tip side) outer peripheral surface of the shaft 11. The movable member 12 is formed in a cylindrical shape or a rectangular tube shape, and the movable member 12 is provided with a hole 12A including a through hole penetrating the center in the axial direction. A female screw 12a that can mesh with the male screw 11a is formed on the inner surface of the hole 12A. However, the inner diameter dimension of the hole 12A is slightly larger than the outer dimension of the shaft 11, and a predetermined clearance (gap) is secured between the male screw 11a and the female screw 12a. For this reason, the shaft 11 has a slight movement margin in a direction perpendicular to the axis in a state where the shaft 11 is inserted into the hole 12A.

  A vibration generating mechanism 20 is provided at the other end of the shaft 11. The vibration generating mechanism 20 shown in this embodiment has a cubic base 13 integrally formed on the other end (base end) of the shaft 11 and a plurality of piezoelectric elements (piezo elements). Yes.

  In this embodiment, four piezoelectric bodies 21, 22, 23, 24 having a thin plate shape are provided perpendicularly to the four side surfaces of the base 13. The four piezoelectric bodies 21, 22, 23, and 24 are formed of thin piezoelectric elements (piezo elements), and a single layer type (monomorph type) in which parallel metal plates forming electrodes are bonded to both surfaces of each piezoelectric element. This is a piezoelectric body.

  The four piezoelectric bodies 21, 22, 23, and 24 can expand and contract in a direction parallel to the surface (a direction orthogonal to the axis of the shaft 11). One end of each of the four piezoelectric bodies 21, 22, 23, and 24 is fixed to one edge of the four side surfaces of the pedestal 13 (the right edge toward the side surface). , 22, 23, 24 are fixed to the fixing portion by a housing (not shown) or the like.

  The four piezoelectric bodies 21, 22, 23, and 24 are driven in synchronism so that all the piezoelectric bodies expand simultaneously and all the piezoelectric bodies contract simultaneously. When all the piezoelectric bodies 21, 22, 23, 24 expand, the shaft 11 is rotated in the α1 direction in FIG. 1, and when all the piezoelectric bodies 21, 22, 23, 24 contract, the shaft 11 1 is rotated in the α2 direction.

  The piezoelectric body may be provided only on a pair of side surfaces that are symmetrical to each other. That is, a configuration in which only the piezoelectric body 21 and the piezoelectric body 22 are provided, or a configuration in which only the piezoelectric body 23 and the piezoelectric body 24 are provided may be employed.

  Next, a drive circuit for driving the actuator 10 and a drive signal supplied from the drive circuit to the actuator 10 will be described.

  2A is a configuration diagram showing a drive circuit of an actuator, FIG. 2B is a waveform diagram showing an embodiment of a drive signal, FIG. 2C is a waveform diagram showing another embodiment of the drive signal, and FIG. 3 is an operation member for the drive signal. It is a figure which shows the relationship between a shaft. In FIG. 3, the white arrow on the outside indicates the position (rotation angle) of the nut, and the black arrow indicates the position (rotation angle) of the shaft.

  As shown in FIG. 2A, the actuator drive circuit 40 includes a constant current source 41, a charging capacitor C1, a discharging semiconductor switch 42, a comparator 43, an amplifying unit 44, and a buffer 45. Is done.

  The capacitor C1 is charged with a constant current supplied from the constant current source 41. At this time, the charging voltage V1 [v] of the capacitor C1 is a linear function (linear) as shown by (i) in FIG. 2B. The comparator 43 compares the charging voltage V1 [v] with the reference voltage Vref [v]. When the charging voltage V1 is less than the reference voltage Vref [v], for example, an L level voltage is output, and the charging voltage V1 is the reference voltage. When Vref or higher, the output is inverted to H level. Further, the semiconductor switch 42 is composed of, for example, an FET or the like, and the state of the switch is switched by receiving an output from the comparator 43. For example, when an L level signal is input to the control terminal (gate terminal G) of the semiconductor switch 42, the switch state is switched from an ON state to an OFF state, and when an H level signal is input, the OFF state is switched to an ON state. Switch to.

  When the semiconductor switch 42 is turned on, the source and drain of the semiconductor switch 42 are short-circuited, so that the charge charged in the capacitor C1 is released at once through the semiconductor switch 42. At this time, as shown by (ii) in FIG. 2B, the charging voltage V1 [v] suddenly reaches 0 [v]. Then, since the charging voltage V1 [v] becomes less than the reference voltage Vref [v], the semiconductor switch 42 is switched to the OFF state. As a result, the source and drain of the semiconductor switch 42 are opened. Therefore, the constant current from the constant current source 41 again flows into the capacitor C1, and the charging voltage V1 is charged until it reaches the reference voltage Vref by a predetermined linear function.

  Then, by repeating the operations (i) and (ii), a sawtooth drive signal S1 as shown in FIG. 2B is generated. The drive signal S1 can be a desired sawtooth wave by appropriately setting the size of the capacitor C1, the magnitude of the constant current, the reference voltage Vref, and the like. Further, if a capacitor is inserted in series before the amplifying unit 44 and the direct current component is cut, the drive signal S1 can have a waveform as shown in FIG. 2C. In the present invention, it is possible to drive the drive signal S1 without making the drive cycle of the drive signal S1 coincide with the intrinsic resonance frequency of the actuator. For this reason, the problem of a decrease in driving efficiency due to frequency deviation can be eliminated.

  The amplifying unit 44 is composed of, for example, a non-inverting amplifier circuit, and a buffer circuit 45 is provided at the subsequent stage. The buffer circuit 45 is composed of, for example, an emitter follower composed of a push-pull of a pair of PNP type transistors and NPN type transistors.

  The amplifying unit 44 amplifies the sawtooth drive signal S1 with a predetermined amplification and supplies the amplified signal to the buffer circuit 45. The buffer circuit 45 supplies necessary electric power to the piezoelectric body in accordance with the amplified drive signal S1. Thereby, the piezoelectric bodies 21, 22, 23, and 24 are expanded or contracted.

  4A to 4D show connection examples of a pair of piezoelectric bodies and a drive circuit. 4A and 4B show a case where the movable member is formed of an insulating member, and FIGS. 4C and 4D show a case where the movable member is formed of a conductive member.

  4A to 4D, the case of the pair of piezoelectric bodies 21 and 22 provided at symmetrical positions will be described. However, the same applies to the case of the pair of piezoelectric bodies 23 and 24. It is given to the piezoelectric body.

  In the connection examples shown in FIGS. 4A to 4D, single layer type piezoelectric bodies 21 and 22 are arranged on a pair of side surfaces provided at symmetrical positions of the movable member 12, respectively.

  The arrows in FIGS. 4A to 4D indicate the polarization directions of the piezoelectric elements. In the following description, the polarization direction from the polarization (−) at the end of the arrow to the polarization (+) at the tip is positive, and the polarization (+) at the tip of the arrow is also from the end. The polarization direction toward the polarization (−) is the negative direction.

  In the first connection example shown in FIG. 4A, one piezoelectric body 21 has the left end portion of the surface on the polarization (+) side fixed to one surface of the pedestal 13. The other piezoelectric body 22 is fixed to the other surface of the pedestal 13, the right end of the polarization (−) side surface being symmetric with the one surface. The output portion 45a of the buffer circuit 45 constituting the drive circuit 40 is provided on the surface of the piezoelectric body 21 on the polarization (−) side and the surface of the piezoelectric body 22 on the polarization (−) side. It is connected to both electrodes 22a. It should be noted that both the electrode 21b provided on the polarization (+) side surface of the piezoelectric body 21 and the electrode 22b provided on the polarization (+) side surface of the piezoelectric body 21 are grounded to the ground GND.

  The drive signal S1 is given from the drive circuit 40 between the electrodes 21a and 21b constituting one piezoelectric body 21 and between the electrodes 22a and 22b constituting the other piezoelectric body 22 at the same timing.

  In the piezoelectric bodies 21 and 22 shown in this embodiment, for example, when the polarization direction of the piezoelectric element coincides with the voltage application direction (both are positive or negative), the piezoelectric bodies 21 and 22 are in the plate thickness direction. A piezoelectric body is used that contracts and expands in the plate thickness direction when the polarization direction of the piezoelectric element is different from the voltage application direction (one is positive and the other is negative).

  For this reason, with respect to the longitudinal direction, which is a direction perpendicular to the plate thickness direction, when the polarization direction of the piezoelectric element coincides with the voltage application direction (when contracting in the plate thickness direction), and when the difference is different (When expanding in the plate thickness direction).

  Therefore, when a periodic signal is given to the piezoelectric bodies 21 and 22 as the drive signal S1, the piezoelectric bodies 21 and 22 repeat expansion and contraction in the longitudinal direction in synchronization with the drive signal S1. For example, as shown in FIG. 4A, when the piezoelectric bodies 21 and 22 both expand in the longitudinal direction, the base 13 and the shaft 11 are rotated in the α1 direction, and both the piezoelectric bodies 21 and 22 contract in the longitudinal direction. The shaft 11 is repeatedly rotated in the α2 direction that is opposite to the α1 direction.

Drive signal S1, in the case of a sawtooth waveform as shown in FIG. 3, when the interval T _A, the voltage the piezoelectric 21 and 22 to be applied in the positive direction is expanded in the longitudinal direction. Also when the interval T _B voltage the piezoelectric 21 and 22 to be applied in the negative direction is contracted in the longitudinal direction. The period _{T A} and the section _{T B,} section _{T B} as compared to the section _{T A} is a relation of a very small _T A >> _{T B.} Therefore, longitudinal displacement of the piezoelectric element 21 expands at a low speed over relatively long time in the interval T _A, in the section T _B shrinks instantaneously (rapidly in a short time) It is driven by so-called forward impact driving.

Incidentally, one cycle of the driving signal S1 is, for example, 0.2 msec, the interval _{T A} in this case 0.19985Msec, interval _{T B} is 150 nsec.

It is no a in FIG. 3 as shown in e, for rotation [alpha] 1 direction the shaft 11 at low speed in the interval T _A, together movable member 12 meshing with shaft 11 in accordance with the rotation of the shaft 11 [alpha] 1 Rotated in the direction. On the other hand, the movable member 12 in the section T _B is reversely rotated to rapidly reversed and α2 direction, in the initial rotating the α2 direction, the movable member 12 in the α1 direction by rotation of the section T _A Inertial force is acting. In addition, a clearance is provided at a portion where the shaft 11 and the movable member 12 are in contact with each other, and a static friction having a large coefficient prevails when rotating at a low speed, and a dynamic friction having a small coefficient is dominant at the time of reversal. It works in the same way. Furthermore, the section T _B for performing reverse operation to the α2 direction is very short, when the movable member 12 is going Hajimeyo rotated to α2 already rotation of the shaft 11 is ended, [alpha] 1 in the next period T _A It is in the stage where rotation in the direction is started.

That is, the movable member 12 is rotated together to follow the shaft 11 to rotate at a low speed in the section T _A, can not follow the rapid inversion operation period T _B In the shaft 11, or not rotate [alpha] 2, Even if it rotates, it becomes a very small amount. Therefore, when the drive signal S1 is input and such a series of operations is repeated, the rotation angle in one direction (α1 direction) of the movable member 12 gradually increases. Note that the movable member 12 does not rotate at all in the other direction (α2 direction) or very little even if rotated. The drive signal S1 is applied to the pair of piezoelectric bodies 21 and 22 and the pair of piezoelectric bodies 21 and 22 are continuously driven, whereby the shaft 11 is rotated in the α1 direction while vibrating.

  When the shaft 11 rotates, a screw feeding operation is performed by meshing between the male screw 11a on the shaft 11 side having a clearance and the female screw 12a on the movable member 12 side. For this reason, the movable member 12 can be moved in the axial direction.

Here the total of the interval T _A and the section T _B as one period of the impact drive. Then, the screw feed amount in one cycle of impact driving, that is, the screw feed amount (amount of movement in the axial direction) when the shaft 11 is reciprocated once is the amount of rotation of the shaft 11 in the α1 direction and the amount of rotation in the α2 direction ( The movable member 12 is moved in the axial direction along the shaft 11 in accordance with the amount of movement. For this reason, it is possible to continuously move the movable member 12 along the axial direction of the shaft 11 (for example, the Z1 direction) by repeating this series of operations and repeating the impact driving to perform rotational vibration. it can.

When it is desired to move the movable member 12 in the reverse direction (for example, the Z2 direction), for example, by giving a drive signal S2 as shown by a one-dot chain line in FIG. Can be rotated. That is, the longitudinal direction of the expansion operation was instantaneously performed in the interval T _B, relatively it may be so causing slowly (reverse impact drive) the contracting operation in the interval T _A.

  Next, in the second connection example shown in FIG. 4B, the end of the electrode 21 a provided on the polarization (−) side surface of the piezoelectric body 21 is fixed to the surface of the base 13. It is different from the connection example. However, the polarization direction of the piezoelectric bodies 21 and 22 and the direction of voltage application are the same in the positive direction.

  Also in this connection example, it is possible to execute the forward impact drive by giving the drive signal S1, and it is possible to execute the impact drive in the reverse direction by giving the drive signal S2. Therefore, similarly to the above, the movable member 12 can be moved in the axial direction along the shaft 11 so as to freely advance and retract.

  Next, the third and fourth connection examples shown in FIGS. 4C and 4D are different in that the pedestal 13 is formed of a conductive material, and the drive signal S1 and the drive signal S2 are supplied through the pedestal 13. To do.

  In the third connection example shown in FIG. 4C, the piezoelectric bodies 21 and 22 are fixed to a pair of symmetrical side surfaces of the pedestal 13 with the same configuration as in the second connection example. That is, the left end portion of the electrode 21 a provided on the polarization (−) side surface of the piezoelectric body 21 is fixed to one side surface of the base 13, and the electrode 22 a provided on the polarization (−) side surface of the piezoelectric body 22. Is fixed to the other side surface of the base 13.

  As shown in FIG. 4C, the output portion 45a of the drive circuit 40 and the pedestal 13 are electrically connected, and the electrode 21b of the piezoelectric body 21 and the electrode 22b of the piezoelectric body 22 are grounded to the ground GND. The polarization direction of the piezoelectric bodies 21 and 22 and the voltage application direction are set in the same direction.

  In the third connection example, the drive signal S1 output from the drive circuit 40 is supplied to the electrode 21a of the piezoelectric body 21 through the pedestal 13 formed of a conductive material, and simultaneously supplied to the electrode 22a of the piezoelectric body 22. The That is, the pedestal 13 can be used as a power receiving terminal or a relay terminal for supplying the drive signal S1 to the electrodes 21a and 22a.

  Next, in the fourth connection example shown in FIG. 4D, the mechanical arrangement relationship between the piezoelectric bodies 21 and 22 and the base 13 is the same as that in the third connection example. However, the fourth connection example is different from the third connection example in that the polarization directions of the piezoelectric bodies 21 and 22 are different from the voltage application direction.

  That is, in the fourth connection example, the output portion 45a of the drive circuit 40 is provided on the electrode 21b provided on the polarization (+) side surface of the piezoelectric body 21 and on the polarization (+) side surface of the piezoelectric body 23. It is electrically connected to both electrodes 22b. The electrode 21 a provided on the polarization (−) side surface of the piezoelectric body 21 and the electrode 22 a provided on the polarization (−) side surface of the piezoelectric body 22 are grounded to the ground GND via the common base 13. Has been.

In the fourth connection example, the drive signal S1 output from the drive circuit 40 is supplied to the electrode 21b of the piezoelectric body 21 and the electrode 22b of the piezoelectric body 22 at the same timing. At this time, the voltage application direction and the polarization direction of the piezoelectric bodies 21 and 22 are in a reverse relationship. Therefore, the interval T _A the piezoelectric 21 and 22 shown in FIG. 3 is caused to relatively slowly shrinking in the longitudinal direction and the piezoelectric 21 and 22 in the section T _B is inflated instantaneously in the longitudinal direction. That is, the piezoelectric bodies 21 and 22 are subjected to impact driving in the opposite direction, and the pedestal 13 and the shaft 11 are rotated in the α2 direction in FIG. 4D. Further, when the drive signal S2 is given, the pedestal 13 and the shaft 11 can be rotated in the α1 direction in FIG. 4D. Therefore, by continuously applying the drive signal S1 or the drive signal S2, the movable member 12 can be moved back and forth in the axial direction along the shaft 11 as described above.

Next, the configuration of the second exemplary embodiment of the present invention will be described.
FIG. 5A is a perspective view of an actuator showing a second embodiment of the present invention, and FIG. 5B is a plan view of FIG. 5A showing a state where a movable member is removed.

  The configuration of the actuator 10 shown in the second embodiment is substantially the same as that of the first embodiment. Therefore, the following description will focus on the different parts. In the second embodiment, the same members as those in the first embodiment will be described with the same reference numerals.

  As shown in FIG. 5A, a cap 12B is provided at the tip of the movable member 12, and the upper end of the hole 12A is closed, which is different from the first embodiment in which the through-hole 12A is exposed. ing. The cap 12B is formed of a convex surface or a hemispherical surface whose tip protrudes toward the tip (Z1) direction. For this reason, even if the tip of the cap 12B comes into contact with any member, the contact area is small, and the coefficient of friction during this time can be reduced, and the rotation of the movable member 12 itself is prevented from stopping. It can be done.

  Next, the difference is that a stopper 11b is provided on the side surface of the shaft 11 and a stopper 12b is provided on the bottom of the movable member 12 on the Z2 side. When the stoppers 11b and 12b are not provided, when the movable member 12 is moved to the base end side (Z2 direction) of the shaft 11, the distal end portion of the male screw 11a and the innermost portion of the female screw 12a are partially There is a possibility that the movable member 12 is locked to the shaft 11 due to the tight engagement. However, when the stoppers 11b and 12b are provided, the stopper 11b and the stopper 12b are engaged with each other before the movable member 12 moves most in the Z2 direction. For this reason, before the male screw 11a and the female screw 12a mesh, the rotation of the movable member 12 can be stopped, and the movement of the movable member 12 can be limited. For this reason, the malfunction that the movable member 12 locks to the shaft 11 can be prevented beforehand. Accordingly, it is possible to prevent a decrease in the driving efficiency of the actuator.

  Furthermore, in the second embodiment, a stacked piezoelectric body 21A formed by sticking a large number of thin piezoelectric elements (piezo elements) in the thickness direction with the polarization directions aligned in the same direction as a whole. The difference is that 22A is adopted. Electrodes are provided at both ends in the longitudinal direction (stacking direction) of the piezoelectric bodies 21A and 22A.

  As shown in FIG. 5A, mounting surfaces 13 </ b> A and 13 </ b> B extending vertically from the respective side surfaces are provided on a pair of opposing side surfaces among the four side surfaces of the pedestal 13. The electrodes provided at one end of the laminated piezoelectric bodies 21A and 22A are fixed to the mounting surfaces 13A and 13B, respectively. The electrodes provided at the other ends of the piezoelectric bodies 21A and 22A are fixed to fixing portions 26 and 26 made of a housing or the like, respectively. The attachment surface 13 </ b> A and the attachment surface 13 </ b> B are provided at positions that are axially symmetric with respect to the shaft 11. Also, one fixing part 26 and the other fixing part 26 are provided at positions opposite to each other. That is, the piezoelectric body 21A is provided between the mounting surface 13A and the one fixing portion 26, and the piezoelectric body 22A is provided between the mounting surface 13B and the other fixing portion 26. The piezoelectric bodies 21A and 22A may be a stacked type in which a large number of thin piezoelectric elements (piezo elements) as shown in FIG. 5A are stacked in the thickness direction and formed into a rod shape, as in the first embodiment. A single layer type in which parallel metal plates forming electrodes are bonded to both surfaces of a thin piezoelectric element may be used.

  When the piezoelectric bodies 21A and 22A are of a single layer type, the vibration generating mechanism can be reduced in size or thickness. On the other hand, in the case of the laminated type, the displacement amount and driving force in the thickness direction of the piezoelectric bodies 21A and 22A as a whole can be made larger than that of the single layer type.

  As described above, the piezoelectric bodies 21A and 22A are driven in synchronism so that the individual piezoelectric elements simultaneously expand or contract simultaneously in the stacking direction. When the piezoelectric bodies 21A and 22A expand, the shaft 11 is rotated in the α1 direction in FIG. 5A, and when the piezoelectric bodies 21A and 22A contract, the shaft 11 is rotated in the α2 direction.

  Therefore, the shaft 11 can be impact driven in the forward direction (α1 direction) or the reverse direction (α2 direction) by continuously applying the drive signal S1 or the drive signal S2 of the piezoelectric bodies 21A and 22A as described above. The movable member 12 can be moved back and forth in the axial direction.

  Further, as shown in FIG. 5B, in addition to the two piezoelectric bodies 21A and 22A, two piezoelectric bodies 23A and 24A having the same configuration are respectively attached to the mounting surfaces 13C and 13D formed at symmetrical positions of the pedestal 13. It may be provided. That is, the four piezoelectric bodies 21A, 22A, 23A, and 24A may be configured so as to be shifted by 90 degrees around the axis of the shaft 11. Also in this case, all the piezoelectric bodies 21A, 22A, 23A, and 24A are given the drive signal S1 or the drive signal S2 at the same timing, thereby being driven in the expanding direction and driven in the contracting direction. . For example, when the drive signal S1 is given to all the piezoelectric bodies 21A, 22A, 23A, 24A at the same timing and the piezoelectric bodies 21A, 22A, 23A, 24A expand, the shaft 11 rotates in the α1 direction in FIG. 5B. Be made. When all the drive signals S2 are given to the piezoelectric bodies 21A, 22A, 23A, 24A at the same timing and the piezoelectric bodies 21A, 22A, 23A, 24A contract, the shaft 11 is rotated in the α2 direction in FIG. 5B. It is done. Thus, when the number of piezoelectric bodies 23A and 24A is increased, the shaft 11 can be driven with a larger driving force.

  In the first and second embodiments, the pedestal 13 that is directly driven by the piezoelectric bodies 21 and 22 on the driving side is shown and described as having a cubic shape, but the present invention is limited to this. Other than that, for example, a triangular prism, a polygonal prism such as a pentagonal prism, or a cylinder may be used. Further, the configuration of the piezoelectric body may not be arranged so as to form a pair at a symmetrical position of the base 13. In other words, any configuration may be used as long as each piezoelectric body provided on the side surface of the base 13 is driven in synchronism with each other so that the driving force from each piezoelectric body acts in the same direction around the axis.

The perspective view of the actuator which shows the 1st Embodiment of this invention, Configuration diagram showing the actuator drive circuit, Waveform diagram showing an embodiment of the drive signal, Waveform diagram showing another embodiment of the drive signal, The figure which shows the relationship between the movable member with respect to a drive signal, and a shaft, The figure which shows the example of a connection of a pair of piezoelectric material and a drive circuit, The figure which shows the example of a connection of a pair of piezoelectric material and a drive circuit, The figure which shows the example of a connection of a pair of piezoelectric material and a drive circuit, The figure which shows the example of a connection of a pair of piezoelectric material and a drive circuit, The perspective view of the actuator which shows the 2nd Embodiment of this invention, The top view of FIG. 5A which shows the state except a movable member,

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Actuator 11 Shaft 11a Male screw 11b Stopper 12 Movable member 12a Female screw 12b Stopper 13 Base 20 Vibration generating mechanism 21, 22, 23, 24 Single layer type piezoelectric body 21A, 22A, 23A, 24A Multilayer type piezoelectric body 26 Fixed portion 40 Drive circuit 41 Constant current source 42 Switch 43 Comparator 44 Amplifier (AMP)
45 Buffer circuit

Claims (7)

A shaft extending in the axial direction and having a male screw on the outer periphery, a movable member formed with a through hole through which the shaft is inserted and meshed with the male screw , a vibration generating mechanism that applies rotational vibration around the shaft axis , and the vibration A drive circuit that drives by generating a predetermined drive signal to the generation mechanism ,
The vibration generating mechanism is provided with a plurality of piezoelectric elements that apply a rotational force in the forward direction and a rotational force in the reverse direction around the axis to the shaft by expansion and contraction, and the same from the drive circuit to the plurality of piezoelectric elements A driving signal is given synchronously, a plurality of the piezoelectric elements expand and contract simultaneously, and a rotational force in the forward direction and a rotational force in the reverse direction are repeatedly applied to the shaft,
One of the time for applying the rotational force in the forward direction and the time for applying the rotational force in the reverse direction is set shorter than the other time, and the movable member is moved in the axial direction. Actuator. Each distal end of the piezoelectric element forming a pair is attached to the base of the shaft, and each proximal end of the piezoelectric element is fixed,
The connecting portion between the tip of one piezoelectric element and the base, and the connecting portion between the tip of the other piezoelectric element and the base are positioned so as to sandwich the axis, and the expansion and contraction directions of the one piezoelectric element and the other piezoelectric element are mutually The actuator according to claim 1, which is parallel . 3. The actuator according to claim 1, wherein the piezoelectric body is a single layer type composed of a single piezoelectric element or a multilayer type in which a plurality of piezoelectric elements are laminated. Each of the piezoelectric elements is plate-shaped, the polarization direction is directed in the plate thickness direction, electrodes are provided on both surfaces, and a conductive pedestal is provided at the base of the shaft. 3. The actuator according to claim 1, wherein the first electrode is electrically connected to the other electrode of the respective piezoelectric elements through a pedestal . The actuator according to any one of claims 1 to 4, wherein the drive circuit includes a charging capacitor, and the driving signal is generated by repeatedly charging and discharging the charging capacitor . Said being internally threaded on the inner surface of the through hole is formed, the actuator according to any one of the claims 1 provided clearance and a radial direction perpendicular to the axial direction between the male thread and the female screw 5 .   The actuator according to any one of claims 1 to 6, wherein stoppers that engage with each other are provided on a base portion of the movable member and an outer surface of the shaft.

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